1. Field of the Invention
The present invention relates generally to medical treatment devices, and, more particularly, to a pulsation treatment apparatus for treating reduced cardiac output in patients.
2. Description of the Related Art
There are a variety of medical conditions in which the heart cannot pump sufficient blood to meet the body's normal requirements for nutrients and oxygen. Congestive heart failure is one such condition in which the heart cannot pump enough blood to meet the needs of the body's other organs. Cardiac output can be too low for a variety of reasons, including coronary artery disease, endocarditis and myocarditis, diabetes, obesity, past heart attacks, high blood pressure, congenital defects, valve disease, or thyroid disease, to name a few. When cardiac output falls, blood returning to the heart through veins can accumulate before it reaches the heart, causing fluid accumulation in the tissues. When cardiac output is too low, the body may take compensatory action including retention of salt by the kidneys. In response to salt retention, the body may retain greater quantities of water to balance sodium, and excess fluids can escape from the circulatory system causing edema (swelling) in other parts of the body. Edema is one of many complications arising from reduced cardiac output and congestive heart failure. The present invention is useful in treating edema, congestive heart failure and reduced cardiac output. Coronary artery disease is another condition that results in insufficient quantities of blood being pumped. Angina pectoris is a condition resulting from coronary artery disease. The present invention is useful in treating both coronary artery disease and angina pectoris.
Various prior art devices have been tried for treating heart patients by means of non-invasive pulsation and counterpulsation. However, the prior art devices typically have delayed response times to changes in the treatment parameter settings. The prior art devices are also limited in their precision of pressure control. These limitations in the prior art devices are serious and unacceptable.
External counterpulsation has developed as a means of treating reduced cardiac output and circulatory disorder stemming from disease. Counterpulsation treatment involves the application of pressure, usually from distal to proximal portions of a patient's extremities, where such application is synchronized with heart rhythms. The treatment augments blood pressure, typically increasing pressure during the diastolic phase of the heart, as such treatment is known to relieve and treat medical conditions associated with reduced cardiac output. Clarence Dennis described an early hydraulic external counterpulsation device and method of its use in U.S. Pat. No. 3,303,841 (Feb. 14, 1967). Dr. Cohen, in American Cardiovascular Journal (30(10) 656-661, 1973) described another device for counterpulsation that made use of balloons which would sequentially inflate and deflate around the limbs of a patient to augment blood pressure. Similar devices using balloons have been described in Chinese patents CN 85200905 (U.S. Pat. No. 4,753,226); Chinese patents CN 88203328, and CN 1057189A.
A series of Zheng patents, including U.S. Pat. No. 4,753,226 (Jun. 28, 1988), U.S. Pat. No. 5,554,103 (Sep. 10, 1996), and U.S. Pat. No. 5,997,540 (Dec. 7, 1999) disclose counterpulsation devices employing sequential inflation of balloon cuffs around the extremities, wherein the cuffs are inflated by a fluid. All three Zheng patents disclose an external counterpulsation device where a series of air bladders are positioned within a rigid or semi-rigid cuff around the legs. The bladders are sequentially inflated and deflated with fluid, such that blood pressure is augmented in the patient. The Zheng '103 and Zheng '540 patents provide for cooled fluid and for monitoring of blood pressure and blood oxygen saturation; however, both retain a similar mechanism dependent on compression of fluid such as air. The Zheng '540 patent modifies the shape of the air bladder and cuffs, but retains a similar mechanism requiring rapid fluid distribution, influx and efflux through balloons in the cuffs.
There are several deficiencies with prior pulsation treatment devices. First, the required circuitous movement of fluid through the apparatus causes a delayed response to changes in pressure settings for the balloons or air bladders. Second, there is also a consequent inability to manipulate action of the cuffs with a high degree of precision. Third, many of the prior art devices require a relatively heavy and noisy compressor and fluid reservoirs for inflating and deflating the cuffs. Fourth, the prior devices lack portability due to their large size and weight, their reliance on a compressor, and their reliance on an electric power source exceeding 120 volt. There are also deficiencies in some of these devices with regard to patients being bounced up and down while undergoing pulsation treatment.
A need therefore exists for a pulsation treatment apparatus that provides very rapid response to changes in applied pressure settings, and that permits control of cuff pressure with a high degree of precision. Preferably, such a treatment apparatus will not require fluid filled balloons or air bladders, or require fluid reservoirs and compressors, and will not subject the patient to undesirable or unnecessary movement. Still more preferably, such a treatment apparatus will be relatively light weight, small, and portable, and will operate on a 120-volt source of electric power.